An add-in prevented this message from being sent. it will be saved as a draft

Products

• Data Loss Prevention Endpoint Prevent
• Data Loss Prevention
• Data Loss Prevention Endpoint Suite
• Data Loss Prevention Enterprise Suite
• Data Loss Prevention Network Email
• Data Loss Prevention Network Monitor and Prevent for Email
• Data Loss Prevention Network Monitor and Prevent for Email and Web
• Data Loss Prevention Network Prevent for Email
• Data Loss Prevention Plus Suite

Issue/Introduction

Users respond to an email and immediately click on the next message; users will receive a pop-up message 

"An add-in prevented this message from being sent. It will be saved as a draft".

The users will need to go to the Draft folder and resend the message once again to be sent. 

 

 

Environment

Release : 15.8 +

Windows O/S Platform

Steps to Reproduce

1. Select an email with an Outlook Preview Pane enabled

2. Reply to the email

3. Immediately select another email

Cause

Customers deployed the "On-Send Web Add-in for Outlook on Windows endpoints due to users having both Windows and MacOS systems 

Deploying the on-send web add-in for Outlook on macOS endpoints

Resolution

1. Upgrade to 16.0 MP1 

Endpoint Fixed Issues in 16.0 MP1

2. If unable to upgrade you can perform the following workaround. 

1. Download and install the Microsoft Administrative templates from Microsoft: Download Administrative Template files (ADMX/ADML) for Microsoft 365 Apps for enterprise/Office LTSC 2021/Office 2019/Office 2016 and the Office Customization Tool for Office 2016 from Official Microsoft Download Center
2. In Group Policy Editor, navigate to User Configuration > Administrative Templates > Microsoft Outlook 2016 > Miscellaneous > Deactivate Outlook web add-ins whose equivalent COM or VSTO add-in is installed
3. Set this to Enabled, and add the following entry:
Value Name: e9c6b99a-5fef-434d-b3e5-f4d5883723b1
Value: Otlk.OutlookAddin
The customer can deploy this via Domain GPO and it should resolve the issue.